Conditional check for “i == (2^8)” fails when i is 512?

Question

Here is a small Program to print powers of 2 till 8. But it is not quitting after 8. Please explain the reason.

#include 
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Answer 1

In C, the ^ operator means XOR (bitwise exclusive or).

To get 2 to the power of 8, you need to either use a loop (res *=2 in a loop), or round the pow function in math.h (note that the math.h function returns float - and therefore won't be equal to the integer).

The simplest method is the bitwise shift, of course.

About the edit section:

Welcome to the wonderful world of operator precedence. What happens is that == has higher precedence than ^, and therefore the conditional evaluates to 2^0, which is 2, which is true.

To make it work, you need to add parentheses:

if ( (2^8) == (1<<8) ) ...